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Over the past 15 years, exotic insects like the Asian longhorned beetle, emerald ash borer (EAB), and hemlock woolly adelgid have killed millions of trees in cities and forests across the United States. Once established in new areas, these pests can quickly kill trees in our favorite forests, parks, communities, and campgrounds. The U.S. Department of Agriculture (USDA) estimates that over 30 million ash trees have already been killed by the emerald ash borer in Michigan alone, with millions dead or dying in other states (see related blog).

Firewood has been shown to be an especially troublesome means by which pests are spread. According to the USDA, the best preventative measure to protect our uninfested urban and rural forests from these pests is to limit the movement of infested materials, including firewood.

Firewood is frequently moved long distances by campers and retailers. Not surprisingly, pest infestations are showing up around campgrounds and highway rest areas. In many states, all trees used as firewood are now regulated since they have the potential to harbor invasive insects and diseases.

Firewood has historically been moved with little consideration of the pests it could be harboring. However, the issue is getting increasing attention. This year, USDA and several states put out urgent pleas to avoid transporting firewood.

Emerald ash borer and its damage to an ash treeImage: National Park Service

To protect forests and trees that are threatened by a host of invasive insects and diseases, regulation has become necessary. While regulations vary by state, they generally include restrictions on importing firewood, the movement of firewood within the state, and the transportation of firewood into state, local and federal parks.

Thirty states have imposed various levels of quarantine as a result of the emerald ash borer. In the Northeast alone, most states have restrictions on the movement of wood products. Other states, including Minnesota, Wisconsin, Michigan, Illinois, Indiana, Kentucky, Ohio, and Maryland, have also imposed regulations on the movement and importation of firewood. Some regulations do not allow the transport of wood beyond a 50-mile radius of an EAB-restricted zone. A restricted zone is the quarantine of an infested area that prohibits the movement of logs and firewood outside of the zone. Check USDA’s quarantine map before you move firewood, even to another town. Because EAB does not travel far on its own, limiting human transportation of infested material will slow its spread.

It is recommended to use locally-sourced firewood, or firewood that has been confirmed as pest free. Firewood producers and dealers must provide documentation on the source of their firewood. Note that seasoned wood alone is not an adequate treatment method because some insects can survive in untreated firewood for many months. Only firewood that is heat treated, kiln-dried (160° F for at least 75 minutes), is allowed to be brought into parks with source documentation.

Be warned that RVs and other vehicles that have been parked for long periods of time can also harbor tree pests and their eggs. If not removed prior to a road trip, these vehicles can introduce pests into a previously uninfested area. So, take the time to check your vehicle, especially the wheel wells, and remove any insects you find. You can also wash down your camper between trips to help remove any hitchhiking pests.

What is at risk from transporting these pests? The trees in your backyard, along your streets, and in your neighborhood, along with the wildlife that depend on them. In addition, jobs in the timber and forestry industries and manufacturing sector (flooring, cabinets, pallets, and even baseball bats) are impacted. A direct consequence to taxpayers are the costs borne by cities and towns to remove the hazardous trees killed by these pests.

Preventing the spread of pests is one component of an Integrated Pest Management program. Doing your part will help sustain the health of our great forest resources and neighborhood trees.

About the Author: Marcia is with EPA’s Center of Expertise for School IPM in Dallas, Texas. She holds a PhD in Environmental Management from Montclair State University along with degrees in Biology, Environmental Design, Landscape Architecture, and Instruction and Curriculum. Marcia was formerly with the EPA Region 2 Pesticides Program and has been a professor of Earth and Environmental Studies, Geology, and Oceanography at several universities.

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I was recently in a conference of Certified Tree Experts representing many northeast and north-central states to discuss the invasion and progressive devastation of our nation’s ash trees by the emerald ash borer.

Yes, we have another pest focused on annihilating our community forests. Think back. First, it was Dutch elm disease. Later, chestnut blight, the gypsy moth, followed by the Asian longhorn beetle. Now, the emerald ash borer (EAB) is here. While common in urban landscapes across much of the continental U.S., native ash trees (Fraxnus sp.) have little natural resistance to this most recent pest. In addition, EAB, which is native to Asia, has no natural enemies in the U.S.

Emerald ash borer adult.Photo: David Cappaert. www.forestryimages.org

A major problem with an emerald ash borer infestation is that most people do not see it coming, and by the time the trees begin to show signs of decline, it is too late. The really bad news is that 95% of ash trees hit with EAB will be dead within five years. The only way to save your favorite ash tree is to prepare and be proactive in your response.

Range. Ground zero for the EAB invasion was near Detroit, Michigan in 2002. EAB has already swept through the Midwest and devastated almost every ash tree in its path. In Ohio, nearly all ash trees (over 20 million) suffered close to 100% mortality. EAB is now present in 34 states and 2 Canadian provinces. In infested areas, 90-100% of ash trees will be dead within 4-5 years.

How does EAB kill trees? EAB attacks ash trees of all sizes. EAB starts with large trees, but then goes down to smaller ones, devouring the insides of every ash tree in its path. EAB first attacks stressed trees, such as those with a portion of bark removed. The females lay 30+ eggs in the cracks of bark, beginning toward the top of the tree. The eggs hatch and the larvae bore in and feed on the phloem that conducts nutrients throughout the tree. Gradually, the infestation moves into the inner layers of the tree. The larvae spend one or two years feeding inside the tree before emerging as adults in the spring. If you see the adults exit holes at eye-level of a tree trunk, the infestation is heavy and has probably been there for several years. Symptoms that aid in early detection are yellowing or orange tinged leaves, loss of leaves in the canopy, sections of death in the canopy and eventually a weak, dying tree.

How does EAB spread to other areas? EAB is often found near highway rest stops. As a matter of fact, as I was driving through Pennsylvania to New Jersey in November, one landed on my car’s windshield at a rest stop. It was the first time I had seen one, and marveled at its small size and metallic green color. EAB’s are carried along railroad and other transportation thoroughfares, wherever ash trees or wood are transported. Adult EABs can hitchhike on truck beds, barges, and cars. Utility workers are often the first to find them in newly infested areas. Female beetles can disperse up to three miles from the source tree.

Emerald ash borer adults.Photo: www.nyis.info

EAB is coming to an ash tree near you. New Jersey, New York, and the New England states are now the latest targets of this pest. According to the New York State Department of Environmental Conservation, less than 5% of the state’s 900 million ash trees are currently infested. However, because black and green ash are keystone species in the regions’ wetland ecosystems, their loss could mean the loss of the entire ecosystem. In New York and New Jersey’s hardwood forests, one in every 10 trees is an ash. The entire state of New Jersey is under an EAB quarantine and under federal and state regulation to minimize the spread to non-infested areas. All ash wood must remain in municipal boundaries unless it is chipped or the bark removed.

Strategies to hamper the spread of EAB. 1) First and foremost quarantine all ash wood, including firewood. 2) Replace ash trees with a diameter of 12” or less. If your community decides not to treat, figure that those ash trees will die, and become hazardous. Do you remove the trees now or later at a higher cost? 3) Remove infected trees – they are already hazardous. Dying trees dry out very fast and become unpredictable because they can crack and fall, even on calm, clear days. Removals should begin with the largest ones first. What to do with all of that ash wood? Chip or kiln dry the wood, which kills the bugs. Ash makes good pellets for wood burning stoves and can also be used in industry, furniture, and baseball bats.

Management options. An Integrated Pest Management (IPM) program for trees helps to create a healthier environment by reducing both pests and unnecessary pesticide use. IPM stresses the use of monitoring, maintenance, and sanitation. The use of pesticides, when needed, is also part of the IPM toolbox. Treating proactively for EAB falls into this “when-needed” category, in lieu of removing all of your ash trees.

If your trees are within 10-15 miles of known infestations, they are at risk. Success in treatment is ultimately determined by both the tree’s health and in initiating treatment before EAB has begun its demise. By the time people notice thinning in the canopy, EAB has already caused considerable damage to the vascular system of the tree. Even large ash trees can be protected from EAB by treating with systemic insecticides. Milwaukee saved most of its trees by treating because they decided that it was more economically beneficial than removal and replacement. Considerations in every town and situation are different.

There are three options for urban ash tree management: Removal and replacement; treatment with insecticides until they can be removed; and treatment with insecticides for the duration of the infestation. New York State and the North Central IPM Center offer good publications that describe the insecticide options for protecting ash trees from EAB. While some options are available to homeowners, others require professional application.

Dr. Jason Graboski of Rutgers University says that the states on the front lines, such as NJ, NY, MD and those in New England can benefit from the lessons learned by MI, OH, IN and PA. He shared with us information from the New Jersey EAB webpage that both informs residents and tracks EAB sitings across the state. New York also has an EAB website with reference maps. In addition, there is a national Emerald Ash Borer Information Network with detailed information for the entire U.S.

About the Author: Marcia is with EPA’s Center of Expertise for School IPM in Dallas, Texas. She holds a PhD in Environmental Management from Montclair State University along with degrees in Biology, Environmental Design, Landscape Architecture, and Instruction and Curriculum. Marcia was formerly with the EPA Region 2 Pesticides Program and has been a professor of Earth and Environmental Studies, Geology, and Oceanography at several universities.

Editor's Note:
The views expressed here are intended to explain EPA policy. They do not change anyone's rights or obligations. You may share this post. However, please do not change the title or the content, or remove EPA’s identity as the author. If you do make substantive changes, please do not attribute the edited title or content to EPA or the author.

EPA's official web site is www.epa.gov. Some links on this page may redirect users from the EPA website to specific content on a non-EPA, third-party site. In doing so, EPA is directing you only to the specific content referenced at the time of publication, not to any other content that may appear on the same webpage or elsewhere on the third-party site, or be added at a later date.

EPA is providing this link for informational purposes only. EPA cannot attest to the accuracy of non-EPA information provided by any third-party sites or any other linked site. EPA does not endorse any non-government websites, companies, internet applications or any policies or information expressed therein.